Aqueous suspension concentrate compositions of pendimethalin

ABSTRACT

The present invention relates to novel stable aqueous suspension concentrate or aqueous flowable compositions of the low-melting dinitroaniline pesticide, pendimethalin, in combination with secondary herbicide(s) melting at temperatures greater than 70° C. or herbicides which are water soluble. Uniquely, pendimethalin may be present in the compositions of the invention in a ratio of orange crystal form to yellow crystal form of 4:96, up to totally orange crystal form. Additionally are provided methods for preparing the compositions containing pendimethalin alone or in combination with the secondary herbicides.

BACKGROUND OF THE INVENTION Related U.S. Application Data

This application is a continuation-in-part of application Ser. No.08/173,809, filed Dec. 27, 1993, now abandoned, which is acontinuation-in-part of two applications, (1) Ser. No. 07/395,925, filedAug. 18, 1989, now U.S. Pat. No. 5,283,231, which is a division ofapplication Ser. No. 07/045,458, filed May 7, 1987, now U.S. Pat. No.4,875,929, which is a continuation-in-part of application Ser. No.06/867,107, filed May 23, 1986, abandoned and (2) Ser. No. 07/385,028,filed Jul. 25, 1989, abandoned, which is a division of application Ser.No. 07/045,457, filed May 7, 1987, now U.S. Pat. No. 4,871,392, which isa continuation-in-part of application Ser. No. 06/867,106, filed May.23, 1986, abandoned.

DESCRIPTION OF THE RELATED ART

Suspension concentrate pesticidal compositions or aqueous flowablecompositions are concentrated suspensions of water-insoluble pesticidesand mixtures of pesticides in an aqueous system. The present inventionrelates to stable pendimethalin compositions.

These aqueous compositions frequently contain about 10% to 80%, byweight, of a solid pesticide or mixture of solid pesticides, therebyproviding a method for handling those pesticides which are relativelywater insoluble in an aqueous medium. Since these types of compositionshave the desirable characteristics of a thick liquid, they may be pouredor pumped. Thus, some of the problems, like dusting that is possible insolid compositions of wettable powders and granulars, are avoided.Further, these aqueous-based concentrates also have the added advantageof not requiring the use of organic solvents, often present inemulsifiable concentrates.

For these reasons, it is desirable to formulate pesticides intosuspension concentrates or aqueous flowables. However, such formulationshave their own problems such as gelling, caking and settling, as well asproblems because of the physical and chemical characteristics of thepesticide or mixture of pesticides. For instance, the dinitroaniline,pendimethalin, is somewhat difficult to formulate and several referenceshave tried to address these formulation problems.

The problems associated with the development of suspension concentratecompositions containing low melting active ingredients, alone or incombination with higher melting active ingredients, are described inGerman Patent Application DE 3302648 A1. German patent Application DE3302648 A1 tries to deal with the problems of an aqueous mixeddispersion of a low melting active ingredient in a solvent of phthalicacid C₁ -C₁₂ alkyl esters in combination with an aqueous suspensionconcentrate containing one or more active ingredients as an alternativeto a suspension concentrate containing low melting active ingredients,such as pendimethalin, N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine!. Thereason for the alternative approach of that application is the inabilityto prepare stable suspension concentrates by various techniques,including those of European Patent Application 0 33291 2. That EPOapplication describes insecticidal suspension concentrate compositionsof phosalone and adjuvants which may be prepared with molteninsecticide. These references do not address ways helpful to thedevelopment of pendimethalin compositions which utilize the orangecrystal form to produce a stable and evenly efficacious product.

Pendimethalin is difficult to formulate not only in a suspensionconcentrate, but in other forms, as well for several reasons. One isthat polymorphic crystals of pendimethalin exist, orange macrocrystalsand yellow microcrystals, with the orange form being dominant.

Not only does pendimethalin exist in two crystal forms, but furthercrystallization occurs when pendimethalin is finally formulated. Theseformulations often exhibit stability problems related to rapid crystalformation of final product. Very large, elongated orange crystals (about3,000 microns in length) are formed in final formulations which resultin instability, difficulty in processing and unreliability in usage.Thus, formulating compositions wherein these elongated crystals do notdevelop is crucial to stability of pendimethalin compositions and isnecessary to obtain even distribution of active compound forapplication.

In formulating pendimethalin in other than suspension concentrates,stabilized pendimethalin had to be used. U.S. Pat. Nos. 4,082,537 and4,150,969 respectively, which disclose compositions containing either asodium dialkyl (C₆ -C₈) sulfosuccinate or an ethoxylated β-diamine,address pendimethalin's unique formulation problems and provide ways toavoid the formation and/or the presence of the larger, orange crystalform. It is believed that the presence of pendimethalin in the orangemacrocrystal form results in large elongated crystals in the finalformulation. These patents describe the use of the sulfosuccinates andthe β-diamines for stabilizing pendimethalin. This technique maintainspendimethalin in the yellow crystal form which does not favor theformation of large elongated crystals in the formulated product for thepreparation of wettable powders. However, these patents fail to discloseways to formulate pendimethalin as a stable suspension concentratecomposition or aqueous flowable composition in the presence of theorange crystal form.

It is an object of the present invention, therefore, to provide stableaqueous suspension concentrate compositions or aqueous flowablecompositions of the low-melting dinitroaniline, pendimethalin, eitheralone or in combination with other pesticides. Although any secondarypesticide may be used, those having higher melting points or pesticideswhich are water soluble are suited to the compositions of thisinvention. Further, it is an additional object of the present inventionto provide methods for preparing such stable aqueous suspensionconcentrate compositions or aqueous flowable compositions so that thefinal compositions do not result in formation of large, elongatedcrystals which interfere with processing and active component efficacyfor application.

It is a further object of this invention to provide stable aqueoussuspension concentrate compositions of pendimethalin having a ratio oforange crystal to yellow crystal of 4:96 to totally (100%) orangecrystal form.

These and other objects will become more apparent by the detaileddescription of the invention provided herein.

SUMMARY OF THE INVENTION

The present invention relates to stable aqueous suspension concentratecompositions or aqueous flowable compositions comprising pendimethalin,alone or in combination with other pesticides. Although most secondarypesticides can be used, those having melting points greater than 70° C.or pesticides which are water soluble are suited in the compositions ofthe invention. Typically, the compositions of the invention comprise, ona weight to volume basis, about 5.0% to 50.0% pendimethalin; about 0% to50.0% of one or more secondary pesticide(s); about 3.0% to 30.0%coformulants, as described in more detail hereinbelow; and about 20.0%to 92.0% water. Preferred compositions provide pendimethalin in acrystal ratio of from about 4:96 of the orange crystal form to theyellow crystal form up to totally (100%) orange crystal form.

The stable compositions of the invention are readily prepared by formingan emulsion of molten pendimethalin in water containing thecoformulants, surfactants, dispersing and/or wetting agents, antifoamingagents and suspending agents. This emulsion has an average droplet sizein a range of less than 2 microns to about 10 microns, preferably 2microns to 6 microns. This is then cooled and optionally milled toobtain an average particle size of suspended particles of less than 20microns, preferably less than 5 microns.

DETAILED DESCRIPTION OF THE INVENTION

Compositions of the invention typically comprise on a weight to volumebasis, about 5.0% to 50.0% pendimethalin; about 0% to 50.0% of one ormore secondary pesticide(s) having a melting point greater than 70° C.or being water soluble; about 3.0% to 30.0% of coformulants, such assurfactants, dispersing agents, wetting agents, antifreezing agents,antifoaming agents, thickening agents, gums, preservatives and 20.0% to92.0% water. Desirably, the pendimethalin in the composition consists ofa crystal ratio wherein 4.0% of the pendimethalin crystals are theorange crystal form, i.e., about 4:96 of the orange crystal form to theyellow crystal form, or the pendimethalin consists of 100% of the orangecrystal form. Most preferred, 10.0% or more of the pendimethalincrystals are the orange crystal form.

Coformulants

Pesticides suitable for use in the composition of the present inventioninclude ureas, triazines, imidazolinones, alone or in combination,amongst just a few. Fungicides, insecticides and plant growth regulatorswhich have melting points greater than 70° C. and/or possess physicalproperties which are amenable to the preparation of aqueous suspensionconcentrate compositions also may be used in the compositions of thepresent invention. Additionally, water-soluble pesticides, such asdifenzoquat, amine salts, alkali or alkali metal salts of ioxynil,bromoxynil, phenoxy acetic acids, and imidazolinyl carboxylic acids suchas2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-quinolinecarboxylicacid and the like may readily be incorporated into the stable aqueoussuspension concentrate compositions of this invention.

Preferred higher melting (greater than 70° C.) components for use in theaqueous suspension compositions of the invention containingpendimethalin include: Isoproturon,N,N-dimethyl-N'-(4-(1-methylethyl)phenyl)urea!; linuron,N-(3,4-dichlorophenyl)-N'-methoxy-N'-methyl urea!; metoxuron,N'-(3-chloro-4-methoxyphenyl)-N,N-dimethylurea!; chlortoluron,N'-(3-chloro-4-methyl-phenyl)-N,N-dimethyl-urea!; diuron,3-(3,4-dichlorophenyl)-1,1-dimethylurea; neburon,N-butyl-N'-(3,4-dichlorophenyl)-N-methylurea; metobromuron,3-(p-bromophenyl)-1-methoxy-1-methylurea; methabenzthiazuron,N-2-benzothiazolyl-N,N'-dimethylurea; imidazolinone herbicides such as2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid or awater soluble salt thereof (e.g., imazapyr, the isopropyl ammonium saltthereof),5-methyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinicacid or a water soluble salt thereof,5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acidor a water soluble salt thereof (e.g., imazethapyr, the ammonium saltthereof),2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-quinolinecarboxylicacid (i.e., imazaquin) and the water soluble salts thereof,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxy-methyl)nicotinicacid and the water soluble salts thereof, and the isomeric mixture ofmethyl 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate andmethyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate (i.e.,imazamethabenz-methyl). Other secondary active components includetriazine herbicides such as atrazine,2-chloro-4-ethyl-amino-6-isopropylamino-1,3,5-triazine!; terbuthylazine,2-tert-butylamino-4-chloro-6-ethylamino-1,3,5-triazine; cyanazine, 2-4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl!amino!-2-methylpropanenitrile;prometryn,N,N'-bis(1-methylethyl)-6-methylthio-1,3,5-triazine-2,4-diamine; andquinmerac, 7-chloro-3-methylquinoline-8-carboxylic acid.

Compositions containing pendimethalin in combination with the secondaryherbicides comprising isoproturon, linuron, metoxuron or chlortoluronare the subject allowed U.S. patent application, Ser. No. 07/395,925filed on Aug. 18, 1989, now U.S. Pat. No. 5,283,231. Compositionscontaining pendimethalin alone are the subject of U.S. Pat. Nos.4,875,929 and 4,871,392.

Surfactants (including dispersing agents and/or wetting agents) suitablein the aqueous suspension compositions of the invention containing solidpendimethalin include: ethylene oxide/propylene oxide condensates;alkyl,aryl- and aryl,arylethoxylates and derivatives thereof;lignosulfonates; cresol- and naphthaleneformaldehyde condensates and thesulfonates thereof; polycarboxylates and derivatives thereof; andmixtures thereof.

In general, anionic polymerics, such as mixtures of alkyl,aryl- andaryl,arylethoxylates and their derivatives, cresol formaldehydecondensates and their sulfonates, naphthalene formaldehyde condensatesand their sulfonates and lignosulfonates have been found to minimizecrystal formation during storage and are preferred surfactants. Themixtures of alkyl,aryl- and aryl,arylethoxylates and their derivativesare most preferred.

Suspending agents such as polysaccharide gums like Xanthangum, guargum;gum arabic and cellulose derivatives, and the like are suitable foraddition to the hot emulsion in amounts of about 0.02% to 3.0%, on aweight to volume basis. These aid in stabilizing the emulsion of adesired droplet size by increasing the viscosity of the emulsion from aninitial viscosity of about 100 cps to about 1,000 cps or greater priorto cooling.

Preservatives to prevent microbial spoiling of the compositions of theinvention are included as necessary. One example is a 38% solution offormaldehyde. Other preservatives include methyl and propylparahydroxybenzoate, 2-bromo-2-nitro-propane-1,3-diol, sodium benzoate,glutaraldehyde, o-phenylphenol, benzisothiazolinone,5-chloro-2-methyl-4-isothiazolin-3-one, pentachlorophenol;2,4-dichlorobenzylalcohol, mixtures thereof and others known to those inthe art. Siliconic antifoaming agents are useful in the presentcompositions.

Antifreezing agents such as ethylene glycol, propylene glycol, otherglycols, glycerine or urea may then be added to the resulting aqueoussuspension concentrate compositions. Additional surfactants,preservatives and thickening agents, such as clays, precipitatedsilicas, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamides andthe like, may then be added, as can higher melting active components ora suspension concentrate containing other active components.

Process of Manufacturing

Stable aqueous suspension concentrate compositions of pendimethalin maybe prepared by a variety of methods which achieve the orange polymorphform of pendimethalin. Preferably, preparation employs moltenpendimethalin, molten so no orange or yellow polymorph is initiallypresent, and then employs a hot emulsion procedure followed by coolingor a hot emulsion procedure with double milling during which conversionto the orange polymorph takes place. For example, a stable compositionmay be prepared by emulsifying molten pendimethalin in hot water (50° C.to 80° C.) containing surfactant(s) and antifoaming agent to achieve thedesired droplet size. Optionally, a suspending agent is added. Theresulting hot emulsion is cooled and agitated, allowing the moltenmaterial to solidify. The resulting composition may then be milled, ifdesired, or additional higher melting active component(s) andcoformulants, such as antifreezing agents, surfactants, thickeners,preservatives and the like or a preformed suspension concentratecontaining one or more active component(s) and coformulants is added.The aqueous suspension concentrate compositions containing pendimethalinin combination with higher melting or water soluble components may thenbe subjected to additional milling, if desired.

The above method of preparation lends itself to a variety of optionalprocessing steps, such as (1) molten emulsion followed by cooling withno further processing; (2) molten emulsion followed by cooling andoptionally adding other active components and coformulants and thenmilling; (3) molten emulsion in the presence of higher melting activecomponents with concurrent milling followed by cooling; (4) moltenemulsion concurrently milled and cooled, then mixing to allowcrystallization and standing ("aging") with or without secondary activecomponents and a second milling.

Alternatively, the molten pendimethalin may be dispersed at ambienttemperature in a water solution of coformulants, containing if desired,other higher melting active components, followed by milling. Stablecompositions may also be obtained by substituting solid pendimethalinhaving at least 4.0% up to 100% in the orange polymorph form in place ofthe molten pendimethalin. For purposes of this invention, ambienttemperature is defined as a temperature of below about 35° C.

Surprisingly, it has been found that stable aqueous suspensionconcentrate compositions of pendimethalin are prepared with at least4.0% of the pendimethalin in the orange crystal form, contrary to whathas been reported previously. In the present invention, pendimethalineven in the large orange crystal form may be used to formulate stableaqueous suspensions. Further, up to 100% of the pendimethalin may bepresent as the orange crystal form whereas only the yellow form wasfavored in the past to avoid large elongated crystals of pendimethalinformulates.

Compositions

Unexpectedly, stable aqueous suspension concentrate compositions ofpendimethalin, alone or in combination with other active pesticidalcomponents may be prepared by the above methods containing, on a weightto volume basis:

5.0% to 50% pendimethalin;

0.05% to 1.0% antifoaming agents;

2.0% to 20.0% antifreezing agents;

2.0% to 20.0% surfactants and mixture of surfactants (wetting anddispersing agents);

0.05% to 3.0% thickening agents;

0.01% to 2.5% preservatives;

0.05% to 2.5% suspending agents; and sufficient water to total 100%.

These compositions do not form large, elongated crystals after beingprocessed. Therefore, processing and manufacturing is not halted becauseof the crystal growths. Further, the compositions are stable withoutsedimentation of active component in these large (3000 micron) crystalsand most importantly, the application of these compositions results inan even dispersibility of active component.

The following examples further illustrate the present invention but arenot limitative thereof.

EXAMPLES 1-23 Method A

preparation of stable aqueous suspension concentrate compositions ofpendimethalin, alone or in combination with other higher meltingherbicides

An aqueous solution containing surfactants and antifoaming agents attemperatures 50° C. to 80° C. is prepared. Then, the moltenpendimethalin (60° C. to 80° C.) is added and agitated sufficiently toobtain an emulsion having an average droplet size of about 2 microns to10 microns. This stabilized emulsion is cooled to ambient temperature,allowing the pendimethalin to solidify, whereupon the desired additionalcoformulants or active components (antifreezing agents, suspendingagents, surfactants, pesticides) are added to the resulting aqueoussuspension of solid pendimethalin.

The resulting aqueous composition is milled to achieve the desiredaverage particle size of suspended particles of less than 20 microns,preferably less than 5 microns; and finally, additional thickeningagents, preservatives or surfactants, as desired, are admixed with theaqueous composition. This is then packaged as the aqueous suspensioncomposition.

Utilizing the above procedure yields the stable aqueous suspensionconcentrate compositions listed in Table I.

                                      TABLE I                                     __________________________________________________________________________             Example                                                              Composition                                                                            1  2  3  4  5  6  7  8  9  10 11 12 13 14 15                         __________________________________________________________________________    Pendimethalin                                                                          26.0                                                                             26.0                                                                             23.6                                                                             20.0                                                                             12.5                                                                             26.0                                                                             26.0                                                                             26.0                                                                             26.0                                                                             26.0                                                                             20.0                                                                             20.0                                                                             26.0                                                                             23.6                                                                             40.0                       (unstabilized)                                                                Isoproturon                                                                            26.0                                                                             26.0                                                                             23.6                                                                             -- 37.5                                                                             -- 26.0                                                                             26.0                                                                             26.0                                                                             26.0                                                                             -- -- 26.0                                                                             23.6                                                                             --                         Chlortoluron                                                                           -- -- -- 30.0                                                                             -- -- -- -- -- -- 30.0                                                                             30.0                                                                             -- -- --                         Isomeric mixture of                                                                    -- -- -- -- -- 12.5                                                                             -- -- -- -- -- -- -- -- --                         methyl 6-(4-                                                                  isopropyl-4-                                                                  methyl-5-oxo-2-                                                               imidazolin-2-yl)-                                                             m-toluate and                                                                 methyl 2-(4-iso-                                                              propyl-4-methyl-5-                                                            oxo-2-imidazolin-2-                                                           yl)-p-toluate                                                                 Na.sup.+ 5.0esol-                                                                         -- 5.0                                                                              -- -- 5.0                                                                              -- -- -- -- -- -- -- -- --                         formaldehyde                                                                  condensate                                                                    Na.sup.+ --resol-                                                                         3.0                                                                              -- 3.0                                                                              3.0                                                                              -- 3.0                                                                              3.0                                                                              3.0                                                                              3.0                                                                              3.0                                                                              3.0                                                                              3.0                                                                              7.0                                                                              5.0                        formaldehyde                                                                  sulphonated                                                                   condensate                                                                    Na.sup.+ 0.5uryl sulfate                                                                  0.5                                                                              0.5                                                                              0.5                                                                              0.5                                                                              -- 0.5                                                                              0.5                                                                              -- -- -- -- 0.5                                                                              -- --                         Ca.sup.++  ligno-                                                                      -- -- -- -- -- 2.0                                                                              2.0                                                                              -- -- -- -- -- -- -- --                         sulfonate                                                                     Alkyl phenol                                                                           -- -- -- -- -- 6.0                                                                              -- -- -- -- -- -- -- -- --                         ethoxylate                                                                    Urea     8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              -- -- 8.0                                                                              -- 8.0                                                                              -- 10.0                                                                             8.0                                                                              --                         Precipitated silica                                                                    2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              2.0                                                                              -- 2.0                                                                              2.0                                                                              2.0                                                                              --                         Xanthan gum                                                                            0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.1                                                                              0.2                                                                              0.12                                                                             0.12                                                                             0.1                                                                              0.2                        Formaldehyde                                                                           0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.25                                                                             0.5                                                                              0.25                                                                             0.25                                                                             0.25                                                                             0.5                        38% solution                                                                  Siliconic antifoam                                                                     0.1                                                                              0.2                                                                              0.5                                                                              0.25                                                                             0.5                                                                              0.75                                                                             0.2                                                                              0.2                                                                              0.2                                                                              0.2                                                                              0.2                                                                              0.2                                                                              0.2                                                                              0.2                                                                              0.2                        Ethylene glycol                                                                        -- -- -- -- -- -- 8.0                                                                              8.0                                                                              -- 8.0                                                                              -- 8.0                                                                              -- -- 8.0                        Ethylene oxide/pro-                                                                    -- -- -- -- -- -- -- -- -- 2.0                                                                              2.0                                                                              2.0                                                                              -- -- --                         pylene oxide                                                                  condensate                                                                    Water    QS QS QS QS QS QS QS QS QS QS QS QS QS QS QS                         __________________________________________________________________________                        Composition                                                                             16 17 18 19 20 21 22 23                         __________________________________________________________________________                        Pendimethalin                                                                           26.0                                                                             20.0                                                                             20.0                                                                             20.0                                                                             20.0                                                                             20.0                                                                             26.0                                                                             26.0                                           Isoproturon                                                                             26.0                                                                             -- -- -- -- -- 26.0                                                                             26.0                                           Chlortoluron                                                                            -- 30.0                                                                             30.0                                                                             30.0                                                                             30.0                                                                             30.0                                                                             -- --                                             Urea      8.0                                                                              -- -- -- -- -- -- 10.0                                           Siliconic antifoam                                                                      0.2                                                                              0.4                                                                              0.5                                                                              0.5                                                                              0.5                                                                              0.5                                                                              0.4                                                                              0.5                                            Xanthan gum                                                                             0.2                                                                              0.05                                                                             -- -- -- 0.05                                                                             -- 0.1                                            Formaldehyde 38%                                                                        0.5                                                                              0.125                                                                            -- -- -- 0.125                                                                            -- 0.25                                           solution                                                                      Precipitated silica                                                                     -- 2.5                                                                              2.0                                                                              -- -- 2.0                                                                              2.7                                                                              2.0                                            Na.sup.+  naphthalene-for-                                                              1.5                                                                              -- -- -- -- -- -- --                                             maldehyde conden-                                                             sate                                                                          Na.sup.+  oleoyl methyl                                                                 1.5                                                                              1.0                                                                              -- -- -- -- -- --                                             tauride                                                                       Ethylene oxide-                                                                         -- 5.5                                                                              2.0                                                                              2.0                                                                              2.0                                                                              3.6                                                                              6.0                                                                              --                                             propylene oxide                                                               copolymer                                                                     Ethylene glycol                                                                         -- 8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              8.0                                                                              --                                             Na.sup.+  cresol-formal-                                                                -- -- 3.0                                                                              3.0                                                                              3.0                                                                              -- -- --                                             dehyde sulfonate                                                              condensate                                                                    Na.sup.+  carboxymethyl                                                                 -- -- 0.5                                                                              -- -- -- -- --                                             cellulose                                                                     Polyvinylalcohol                                                                        -- -- -- 2.0                                                                              -- -- -- --                                             Polyvinylpyrrolidone                                                                    -- -- -- -- 2.0                                                                              -- -- --                                             Na.sup.+  lignosulfonate                                                                -- -- -- -- -- 2.0                                                                              -- --                                             China clay                                                                              -- -- -- -- -- -- 1.3                                                                              --                                             Calcium chloride                                                                        -- -- -- -- -- -- 1.3                                                                              --                                             Na.sup.+  polyacrylate                                                                  -- -- -- -- -- -- -- 2.0                                            Propoxylated alkyl-                                                           aryl ethoxylate                                                                         -- -- -- -- -- -- -- 3.0                                            Water     Sufficient water to total                       __________________________________________________________________________                                  100%                                        

EXAMPLES 24-44 Method B

Preparation of stable aqueous suspension concentrate compositions ofpendimethalin, alone or in combination with other active components

An aqueous solution containing surfactant(s) and antifoaming agents isprepared at a temperature of 50° C. to 80° C. Then, the moltenpendimethalin (60° C. to 80° C.) added to the aqueous solution whileagitating sufficiently to obtain an emulsion having an average dropletsize of about 2 microns to 10 microns. Sufficient suspending agent isadded to this to stabilize the thus-formed emulsion, and this is cooledto ambient temperature, allowing the pendimethalin to solidify,whereupon the additional coformulants, as desired, are admixed to theresulting suspension. This can then be packaged.

Further, a suspension of a pesticide having a melting point greater than70° C. is prepared and milled to a suitable average particle size (i.e.,less than 20 microns, preferably less than 5 microns) or an aqueoussolution containing the desired amount of a water-soluble pesticide isprepared.

Either one of these is then admixed with the suspension concentratecomposition of pendimethalin prepared hereinabove. Finally, additionalthickening agents, preservatives or surfactants, as desired, are added,and this is then packaged as the mixed aqueous suspension concentratecomposition.

Utilizing the above procedure yields the stable aqueous suspensionconcentrate compositions listed in Table II.

                  TABLE II                                                        ______________________________________                                                        Example                                                       Composition       24     25     26   27   28                                  ______________________________________                                        Pendimethalin (unstabilized)                                                                    23.6   23.6   23.6 23.6 23.6                                Isoproturon       23.6   23.6   23.6 23.6 23.6                                Na.sup.+  cresol-formaldehyde                                                                   --     3.0    4.1  3.0  4.3                                 sulfonated condensate                                                         Na.sup.+  cresol-formaldehyde condensate                                                        5.0    --     --   --   --                                  Alkyl phenol ethoxylate                                                                         --     --     --   --   8.0                                 Na.sup.+  oleoyl methyl tauride                                                                 --     0.65   --   --   --                                  Na.sup.+  lauryl sulfate                                                                        0.5    --     --   0.5  --                                  Urea              8.0    8.0    8.0  --   8.0                                 Ethylene glycol   --     --     --   8.0  --                                  Blend of polyalkylene glycol ether                                                              --     --     0.7  --   --                                  and polyoxyethylene alkylaryl ether                                           Siliconic antifoam                                                                              0.25   0.5    0.5  0.5  0.5                                 Silica            2.0    2.0    --   2.0  --                                  Xanthan gum       0.1    0.1    0.2  0.1  0.1                                 Formaldehyde 38% solution                                                                       0.25   0.25   0.5  0.25 0.3                                 Water             QS     QS     QS   QS   QS                                  ______________________________________                                                        Example                                                       Composition       29     30     31   32   33                                  ______________________________________                                        Pendimethalin (unstabilized)                                                                    20.0   20.0   20.0 26.0 30.0                                Chlortoluron      30.0   30.0   --   --   --                                  Isomeric mixture of methyl 6-(4-iso-                                                            --     --     12.5 12.5 --                                  propyl-4-methyl-5-oxo-2-imidazolin-                                           2-yl)-m-toluate and methyl 2-(4-iso-                                          propyl-4-methyl-5-oxo-2-imidazolin-                                           2-yl)-p-toluate                                                               Ammonium 2-(4-isopropyl-4-methyl-                                                               --     --     --   --   5.0                                 5-oxo-2-imidazolin-2-yl)-3-quino-                                             linecarboxylic acid (solution)                                                Na.sup.+  cresol-formaldehyde sulfonated                                                        3.0    3.6    --   --   --                                  condensate                                                                    Na.sup.+  cresol-formaldehyde condensate                                                        --     --     5.0  3.0  --                                  Triethanolamine salt of polyarylaryl-                                                           --     --     --   1.3  --                                  ethoxylate phosphate                                                          Na.sup.+  lignosulfonate                                                                        --     --     --   --   4.0                                 Ca.sup.+  lignosulfonate                                                                        --     --     2.0  --   --                                  Alkyl phenol ethoxylate                                                                         --     --     8.0  6.0  --                                  Na.sup.+  lauryl sulfate                                                                        0.5    --     --   --   --                                  Urea              8.0    8.0    8.0  --   --                                  Ethylene glycol   --     --     --   5.0  8.0                                 Siliconic antifoam                                                                              0.5    0.1    0.5  0.4  0.5                                 Silica            2.0    0.1    2.0  2.0  0.75                                Xanthan gum       0.1    0.2    0.1  0.1  0.1                                 Formaldehyde 38% solution                                                                       0.25   0.5    0.25 0.25 0.25                                Glacial acetic acid (to pH 7.4)                                                                 --     --     --   --   .check mark.                        Blend of polyalkylene glycol ether                                                              --     0.55   --   --   --                                  and polyoxyethylene alkylaryl ether                                           Water             QS     QS     QS   QS   QS                                  ______________________________________                                                     Example                                                          Composition    34     35     36   37   38   39                                ______________________________________                                        Pendimethalin (unstabilized)                                                                 33.0   40.0   40.0 40.0 40.0 33.0                              Na.sup.+  cresol-formaldehyde                                                 sulfonated condensate                                                                        --     4.2    --   --   --   --                                Na.sup.+  cresol-formaldehyde                                                                --     --     4.7  --   --   4.2                               condensate                                                                    Triethanolamine salt of poly-                                                                3.4    --     --   --   --   --                                arylarylethoxylate phosphate                                                  Na.sup.+  lignosulfonate                                                                     --     --     --   4.8  --   --                                Urea           --     --     --   --   --   13.3                              Ethylene glycol                                                                              8.0    8.0    --   --   5.0  --                                Siliconic antifoam                                                                           0.1    0.5    0.9  0.3  1.0  0.3                               Xanthan gum    0.1    0.1    0.1  0.1  0.2  0.16                              Formaldehyde 38% solution                                                                    0.25   0.25   0.25 0.25 0.5  0.4                               Polycarboxylate derivative                                                                   --     --     --   --   3.0  --                                Water          QS     QS     QS   QS   QS   QS                                ______________________________________                                        Composition       40     41     42   43   44                                  ______________________________________                                        Pendimethalin (unstabilized)                                                                    27.3   30.0   27.3 30.0 30.0                                Atrazine          18.2   20.0   18.2 20.0 20.0                                Na.sup.+  cresol-formaldehyde sulfonated                                                        3.4    1.65   3.4  1.65 1.65                                condensate                                                                    Triethanolamine salt of polyarylaryl-                                                           --     --     --   1.9  1.9                                 ethoxylate phosphate                                                          Urea              5.8    --     --   --   50                                  Ethylene glycol   --     5.6    5.2  5.0  --                                  Blend of polyalkylene glycol ether                                                              1.34   1.26   1.2  --   --                                  and polyoxyethylene alkylaryl ether                                           Siliconic antifoam                                                                              0.9    0.35   0.9  0.16 0.16                                Silica            --     0.5    --   0.4  0.4                                 Xanthan gum       0.2    0.1    0.2  0.1  0.1                                 Formaldehyde 38% solution                                                                       0.5    0.25   0.5  0.25 0.25                                Water             QS     QS     QS   QS   QS                                  ______________________________________                                    

EXAMPLES 45 and 46 Method C

Preparation of stable aqueous suspension concentrate compositions

An aqueous dispersion of surfactants, antifoaming and antifreezingagents, containing, if desired, a solid active component having amelting point greater than 70° C., is prepared or a water soluble activecomponent is prepared at ambient temperatures. The molten pendimethalin(60° C. to 80° C.), with or without additional surfactants, is thenadded to the agitated aqueous mixture. This resulting aqueous mixture ismilled to achieve the desired average particle size of suspended solids,less than 20 microns, preferably less than 5 microns, and additionalthickening agents, suspending agents, preservatives, antifreezing agentsand surfactants, as desired, are admixed to the milled composition. Thisis then packaged as the resulting stable aqueous suspension concentratecomposition.

Utilizing the above procedure yield the stable aqueous concentratecompositions listed in Table III.

                  TABLE III                                                       ______________________________________                                                               Example                                                Composition              45     46                                            ______________________________________                                        Pendimethalin (unstabilized)                                                                           26.0   26.0                                          Isoproturon              26.0   26.0                                          Na.sup.+  cresol-formaldehyde sulfonated condensate                                                    3.0    --                                            Polyarylarylpolyoxyethylene phosphate, acid form                                                       --     5.0                                           Siliconic antifoam       0.2    0.2                                           Xanthan gum              0.2     0.12                                         Formaldehyde 38% solution                                                                              0.5    0.5                                           Ethanediol (Ethylene glycol)                                                                           8.0    --                                            Water                    QS     QS                                            ______________________________________                                    

EXAMPLES 47 and 48 Methods A and E

Preparation of stable aqueous suspension concentrates of pendimethalinvia the method of the invention versus the method of milling whilecooling an emulsion (Method E)

An aqueous suspension concentrate composition of pendimethalin isprepared according to Examples 1-23, Method A. As a comparison, asuspension concentrate of pendimethalin is prepared according to thedescription of EPO Application 033291.2.

A mixture of hot water (575 cc), ethylene glycol (50 g) and an anionicsurface-active agent (a mixture of the monophosphate and the diphosphateof tristyrylphenol with a polyoxyethylene of 18 oxyethylene units,neutralized with triethanolamine, marketed under the tradename ofSOPROPHOR FL® by Rhone-Poulenc) (50 g) is vigorously agitated while 400g of pendimethalin are added. This is then ground in a Dyno Mill with ajacket for rapid cooling, resulting in a mixture leaving the mill at 24°C. and having a particle size of 98% less than 5 microns, indicating theformation of a suspension concentrate.

A Xanthan gum biopolymer of a heteropolysaccharide type (1.5 g),produced by fermentation of Xanthomonas campestris on carbohydrates(tradename RHODOPOL® XB 23 marketed by Rhone-Poulenc), is added.

Table IV summarizes the stability observations of the two compositions.The milling method does not avoid the appearance of elongated crystalseven upon two short periods of storage, one three day storage at 15° C.and one three day storage at 28° C.

                                      TABLE IV                                    __________________________________________________________________________    Method A - Method of the Invention                                                                 Method E - Milling while cooling*                        Composition                                                                            % w/v                                                                             Result  Composition                                                                             % w/w                                                                             Result                                     __________________________________________________________________________    Pendimethalin                                                                          40.0                                                                              After six weeks                                                                       Pendimethalin                                                                           40.0                                                                              Two tests:                                              at 28°C., 95% of                                                                             Large crystals                                          the particles                                                                         Suspending agent                                                                        0.15                                                                              particle size                              Suspending agent                                                                       0.02                                                                              have an average                                                                       Xanthan gum   up to 80 × 5                         Xanthan gum  particle size of                                                                      (added after  microns ap-                                (added prior less than 15 × 4                                                                milling and   peared after                               to cooling)  microns.                                                                              cooling)      three days at                              Surfactants                                                                            4.0                       15° C. and also                     Sulfonated cresol-   Surfactants                                                                             5.0 when stored at                             formaldehyde con-    mixture of mono-                                                                            three days at                              densate              and di-phosphate                                                                            28° C.                              Polyethoxylated-                                                                       3.0         of tristyrylphenol                                       polymethylmeth-      neutralized with                                         acrylate             triethanolamine                                          Antifreeze                                                                             5.0         (SOPROPHOR ®FL)                                      Urea                 Antifreeze                                                                              5.0                                            Antifoam 0.5         Ethylene glycol                                          Siliconic                                                                     Preservative                                                                           0.1                                                                  Benzisothiazolone                                                             __________________________________________________________________________     ®Trademark of Soprosie, Division od RhonePoulenc.                         *Particle size found in initial suspension concentrate composition is 98%     less than five (5) microns.                                              

EXAMPLES 49-50

Compositions containing active compound of the invention

An aqueous suspension concentrate composition of pendimethalin with asecondary pesticide is prepared according to Examples 1-23 containingthe following components:

    ______________________________________                                                        (% w/v)                                                                       Formula X                                                                            Formula Y                                              ______________________________________                                        Pendimethalin     23.6     20.0                                               Isoproturon       23.6     --                                                 Chlortoluron      --       --                                                 Na cresol-formaldehyde                                                                          4.1       4.14                                              sulphonated condensate                                                        surfactant                                                                    Polycarboxylate   --        1.64                                              surfactant                                                                    Blend of polyalkylene                                                                            0.71    --                                                 glycol ether and                                                              polyoxyethylene alkyl                                                         aryl ether                                                                    Urea              8.0      8.0                                                Xanthan gum       0.2      0.2                                                30% siliconic antifoam                                                                          0.5      0.3                                                Benzisothiazolinone                                                                             --        0.033                                             Methyl paraben    0.1      --                                                 Propyl paraben     0.05    --                                                 Water To          100.00%  100.00%                                            ______________________________________                                    

EXAMPLES 51-52

Compositions using hot emulsion double milling process

A hot emulsion of molten pendimethalin is prepared as in Examples 1-23wherein hot pendimethalin is added to the hot solution of surfactantwhilst mixing at highshear. The temperature is 50° C. to 80° C. with aparticle size of 2μ to 5μ. The hot emulsion is then milled through aDyno-Mill and exits as a shattered crystalline form (temperature intomill is about 65° C., and temperature exiting is about 20° C. to 25°C.). This mixture is allowed to "age" to allow orange polymorph crystalconversion. Following conversion, usually 0.5 to 48 hours, a secondmilling in a Dyno-Mill occurs. (In the event another active pesticide isadded, it is added into the aging period stage). Once milled a secondtime, final coformulants are added.

The following compositions are prepared according to the aboveprocedures.

    ______________________________________                                                           Concentrate                                                ______________________________________                                                             % w/w                                                    Pendimethalin technical                                                                            40.0                                                     SOPROPHOR ® FL surfactant                                                                      5.0                                                      SILCOLAPSE ® 5000                                                                              0.5                                                      Propylene glycol     7.0                                                      Water To             100.0%                                                   This is formulated into the following:                                                             g/L                                                      Concentrate from above                                                                             1000                                                     RHODOPOL ® 2% gel                                                                               70                                                      Water To             .sup.  100%                                                                   % w/v                                                    Concentrate from above                                                                             75.0                                                     Atrazine technical   20.0                                                     SOPROPHOR ® FL   1.25                                                     Propylene glycol     1.25                                                     Water To             100.00%                                                  ______________________________________                                    

EXAMPLES 53-61

Preparation of stable aqueous suspension concentrate compositions ofpendimethalin with orange crystal form

An aqueous solution containing 'surfactant(s), antifoaming agents and,if desired, secondary water soluble pesticides is prepared at ambienttemperatures. Solid pendimethalin, having a minimum of 4.0% of theorange crystal form, is added, and any other solid secondary pesticidehaving a melting point greater than 70° C. may also be added.

The mixture is milled to achieve the desired average particle size ofsuspended particles of less than 20 microns, preferably less than 6microns (2 microns to 6 microns). Then, thickening agents, suspendingagents, antifreezing agents, preservatives and additional surfactantsare admixed with the resulting mixture to produce a stable aqueoussuspension concentrate composition.

Utilizing the above procedure, the stable aqueous suspension concentratecompositions listed in Table V are prepared.

                                      TABLE V                                     __________________________________________________________________________               Example                                                            Composition                                                                              53  54  55  56  57  58  59  60  61                                 __________________________________________________________________________    Pendimethalin                                                                            23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              20.0                                                                              44.8                               (orange/yellow ratio)                                                                    (32/68)                                                                           (32/68)                                                                           (32/68)                                                                           (24/76)                                                                           (16/84)                                                                           (8/92)                                                                            (4/96)                                                                            (46/54)                                                                           (100%)                             Isoproturon                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              23.6                                                                              --  --                                 Chlortoluron                                                                             --  --  --  --  --  --  --  30.0                                                                              --                                 Na.sup.+  cresol-formaldehyde                                                            3.0 3.0 --  3.0 3.0 3.0 3.0 3.0 --                                 sulfonated condensate                                                         Na.sup.+  naphthalene sul-                                                               --  --  --  --  --  --  --  --  3.0                                fonated condensate                                                            Ethylene oxide - pro-                                                                    2.0 --  --  --  --  --  --  2.0 --                                 pylene oxide copolymer                                                        Na.sup.+  lauryl sulfate                                                                 --  0.5 --  0.5 0.5 0.5 0.5 --  --                                 Triethanolamine salt of                                                       polyarylarylethylene                                                                     --  --  3.0 --  --  --  --  --  --                                 oxide phosphate                                                               Ethylene glycol                                                                          8.0 --  8.0 8.0 8.0 8.0 8.0 8.0 3.0                                Urea       --  8.0 --  --  --  --  --  --  --                                 Silica     2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 0.8                                Siliconic antifoam                                                                       0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 --                                 Formaldehyde                                                                  38% solution                                                                             0.125                                                                             0.25                                                                              0.25                                                                              0.25                                                                              0.25                                                                              0.25                                                                              0.25                                                                              0.25                                                                              --                                 Xanthan gum                                                                              0.05                                                                              0.1 0.1 0.1 0.1 0.1 0.1 0.05                                                                              --                                 Water      QS  QS  QS  QS  QS  QS  QS  QS  QS                                 __________________________________________________________________________

What is claimed is:
 1. A stable aqueous suspension concentratecomposition consisting essentially of, on a weight to volume basis:about 5.0% to 50.0% solid pendimethalin; up to about 50.0% of at leastone or more secondary herbicide(s); about 3.0% to 30.0% coformulantselected from the group consisting of a surfactant, a dispersing agent,a wetting agent, a suspending agent, an antifreezing agent, anantifoaming agent, a thickening agent and a preservative; and about20.0% to 92.0% water, wherein the pendimethalin contains, on a weight toweight basis, from about 4.0% to 100% orange crystal form and from about0 to 96% yellow crystal form; the secondary herbicide is diuron,neburon, metobromuron, methabenzthiazuron, prometryn, atrazine,terbuthylazine, cyanazine, quinmerac,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid or awater soluble saltthereof,5-methyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinicacid or a water soluble salt thereof,5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acidor a water soluble salt thereof,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-quinolinecarboxylicacid or a water soluble salt thereof,2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-(methoxymethyl)nicotinicacid or a water soluble salt thereof, or an isomeric mixture of methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate andmethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate andthe surfactant, dispersing agent and wetting agent are selected from thegroup consisting of an ethylene oxide/propylene oxide condensate; analkyl, aryl-ethoxylate, an aryl, aryl-ethoxylate or a derivativethereof; a lignosulfonate; a cresol-formaldehyde condensate; asulfonated cresol-formaldehyde condensate; a naphthalene-formaldehydecondensate; a sulfonated naphthalene-formaldehyde condensate; apolycarboxylate or a derivative thereof; and a mixture thereof.
 2. Thecomposition according to claim 1, wherein the secondary herbicide iswater soluble or has a melting point greater than 70° C.
 3. Thecomposition according to claim 1, wherein the surfactant is atriethanolamine or potassium salt of polyarylarylethoxylate phosphate ora polyarylarylpolyoxyethylene phosphoric acid.
 4. The compositionaccording to claim 1 wherein the suspending agent is a polysaccharidegum of a cellulose derivative.
 5. The composition according to claim 4,wherein the polysaccharide gum is Xanthan gum, guar gum, gum arabic or amixture thereof.
 6. The composition according to claim 5, wherein theantifreezing agent is ethylene glycol, propylene glycol, glycerine, ureaor a mixture thereof.
 7. The composition according to claim 6, whereinthe thickening agent is a clay, a precipitated silica, polyvinylalcohol, polyvinylpyrrolidone, polyacrylamide or a mixture thereof. 8.The composition according to claim 7, wherein the antifoaming agent is asiliconic antifoaming agent.
 9. The composition according to claim 8,wherein the preservative is a 38% formaldehyde solution, methyl orpropyl parahydroxybenzoate, 2-bromo-2-nitro-propane-1,3-diol, sodiumbenzoate, glutaraldehyde, o-phenylphenol, benzisothiazolinone,5-chloro-2-methyl-4-isothiazxolin-3-one, pentachlorphenol,2,4-dichlorobenzylalcohol or a mixture thereof.
 10. The compositionaccording to claim 9, comprising, on a weight to volume basis: about5.0% to 50.0% pendimethalin, up to about 50.0% of the secondaryherbicide, about 2.0% to 20.0% surfactant, about 0.05% to 2.5%suspending agent, about 2.0% to 20.0% antifreezing agent, about 0.05% to1.0% antifoaming agent, about 0.05% to 2.0% thickening agent and about0.05% to 2.5% preservative.
 11. The composition according to claim 10,comprising, on a weight to volume basis: 27.3% pendimethalin, 18.2%atrazine, 3.4% sodium salt of sulfonated cresol-formaldehyde condensate,5.8% urea, 1.34% polyalkylene glycol ether and polyoxyethylene alkylarylether, 0.9% siliconic antifoaming agent, 0.2% Xanthan gum, 0.5% of a 38%formaldehyde solution and 48.9% water.
 12. The composition according toclaim 10, comprising, on a weight to volume basis: 30.0% pendimethalin,5.0% of the water soluble ammonium salt of2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-quinolinecarboxylicacid, 4.0% sodium lignosulfonate, 8.0% ethylene glycol, 0.5% siliconicantifoaming agent, 0.75% silica, 0.2% Xanthan gum, 0.25% of a 38.0%formaldehyde solution and 58.1% water.
 13. The composition according toclaim 10, comprising, on a weight to volume basis: 26.0% pendimethalin,12.5% of an isomeric mixture of methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and andmethyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate, 3.0%sodium salt of sulfonated cresol-formaldehyde condensate, 1.3%triethanolamine salt of polyarylarylethoxylate phosphate, 6.0%alkylphenol-ethoxylate, 5.0% ethylene glycol, 0.4% siliconic antifoamingagent, 2.0% silica, 0.1% Xanthangum, 0.25% of a 38% formaldehydesolution and 49.62% water.